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Interaction of a Crack with Crystal Defects

裂纹与晶体缺陷的相互作用

基本信息

批准号：
06650726
负责人：
NARITA Nobutaka
金额：
$ 1.34万
依托单位：
KYOTO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1994
资助国家：
日本
起止时间：
1994 至 1995
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-06650726/
关键词：
Crack Crystal defect Dislocation Fracture toughness Embrittlement Fracture

项目摘要

Interactions of a crack with mobile defects such as dislocations and interstitial impurities were investigated with particular attention to the effect of defect redistribution on crack extension. The fracture toughness K_<IC> in NaCl crystals is gradually decreased with increasing temperature in the range below room temperature. At above room temperature, The values of K_<IC> are increased with increasing temperature. Computer aimulation showed that at low temperatures anti-shielding dislocations generated from internal sources are more active and serve to decrease K_<IC> values with increasing temperature, while at high temperatures shielding dislocations are much emitted from a crack tip by thermal activation and cause to increase K_<IC> values. This tendenccy is consistent with the observed dependence of K_<IC> values, but there are some quantitative differences between computed and experimental results. Photo-elastic observations showed that those differences are caused by crack tip blunting as well as the stabilization of dislocation structures. In case of mobile interstitial impurities in iron alloy crystals, the impurities distributed ahead of a crack tip intensify the local k field to promote crack extension so as to decrease K_<IC> values. The forward impurity distribution is enhanced by the tetragonal strain of impurity atoms and also by the mutual interaction of impurities under the presence of a crack. The promotion of crack extension by mobile impurities was verified using the plasma charging of impurities into Fe-Si alloy crystals.

研究了裂纹与诸如位错和间隙杂质等移动的缺陷的相互作用，特别注意缺陷再分布对裂纹扩展的影响。在<IC>室温以下的温度范围内，NaCl晶体的断裂韧性K_（max）随温度的升高而逐渐降低。在室温以上，K_（？）值<IC>随温度的升高而增大。计算机模拟结果表明，在低温下，由内源产生的反屏蔽位错更活跃，随温度升高而降低K<IC>值，而在高温下，屏蔽位错因热激活而从裂纹尖端大量发射，使K值升高<IC>。这一趋势与K值随时间的变化规律一致<IC>，但计算值与实验值之间存在一定的定量差异。光弹性观测表明，这些差异是由裂纹尖端钝化以及位错结构的稳定化引起的。当铁合金晶体中存在移动的间隙杂质时，分布在裂纹尖端前方的杂质强化了局部k场，促进裂纹扩展，从而降低K<IC>值。杂质原子的四角应变和裂纹存在下杂质的相互作用增强了正向杂质分布。利用等离子体向Fe-Si合金晶体中充入杂质，验证了移动的杂质对裂纹扩展的促进作用。